Forming of metals



May 2l, 1963 J. KARPovlcH 3,090,113

FORMING OF METALS Filed NOV. 1'?, 1960 L fg u/'a/ con /a/'n er INVENTOR. Jo/n Kar/oowc 3,696,113 FORMNG 0l? METALS .Fehn Karper/ich, Midiand, Mich., assigner to The Daw Chemical Company, Midiand, Mich., a corporation of Deiaware Filed Nov. 17, 219156, Ser. No. 69,895 6 Claims. (Cl. 29-42i) This invention relates to metal forming and more particularly is concerned with a method for the forming of metals by means of ballistically generated shock waves.

It is a principal object of the present invention to provide a new and novel method of forming metals which is both safe and relatively inexpensive.

It is a further object of the present invention to provide a simple means of forming widely diversiiied metal shapes.

It is an additional object of the present invention to provide a means of applying high energy to a metal being formed without the use of hydraulic presses and other conventional heavy-duty equipment.

These and other objects and advantages will be apparent from the detailed description presented hereinafter and by reference to the accompanying drawing.

The FIGURE in the drawing shows one general method of carry-ing out metal forming by the method of the instant invention.

In general this method of ballistically forming comprises immersing a mold within a liquid, positioning a metal to be formed adjacent to the mold and passing a high velocity projectile through the liquid, the metal to be formed being between the projectile and the mold surface. This metal thereby is subjected to shock Waves formed in the liquid by the high velocity projectile and in the forming operation is forced into conformity with the shape of the mold. In this operation, .the shock wave may be visualized as acting as the male member of a conventional press or forming apparatus.

The actual forming is achieved primarily from the energy contained in the shock front formed at the front tip or nose of the projectile and by the cavities generated in 'the liquid behind the moving body. As the forward par-t of the projectile penetrates the liquid, it fractures the liquid as well as causes it to dynamically compress thereby setting up a shock wave front in the liquid. At the same time, vacuum pockets, or cavities, are formed in the liquid immediately behind the projectile. These cavities, soon after formation, collapse violently thereby releasing a second series of shock waves which propagate throughout the liquid medium and augment the shock wave front of the projectile .thereby giving added energy to the metal forming operation.

Any one of a wide variety of projectiles or bodies can be used in the instant method of forming, the critical feature of the process being that this body penetrate the liquid, containing the mold and the metal to be formed, with energy sufcient to produce a shock front in this liquid along with cavitation of the liquid behind the moving projectile.

Particularly useful means of carrying out the method of the instant invention include, for example, tiring a gun, Le., introduction of a small arm bullet, rilie bullet or shotgun slug into the liquid lcontaining the mold and metal, using high pressure gas to propel a projectile into the forming bath, detonating a metal-lined shaped charge into the fluid, mechanically accelerating a sphere, teardrop, or other shaped projectile so that it passes in the vicinity of the metal, and other conventional means of propelling a mass so that the desired shock front and liquid cavitation are formed.

The metal forming eliectiveness of any specilic pr'ojectile or body, for example, a rie bullet, shotgun slug 3,9%,ll37 Patented May 2i, i963 or .the like is dependent, among other factors, on the size of the iluid container which holds the mold assembly and into fwhich this projectile is red. The greater the distance between the side walls of the container the more energy that must be imparted to the fluid by the projectile to insure satisfactory forming of the metal. To illustrate, a sheet of 0.012 inch aluminum Was attached to a hat mold having a hole punched therein. This assembly was placed in a 6 inch diameter cylindrical tank filled with rwater and a 30-06 rifle tired so that the bullet (projectile) passed vertically downward through the container. Excellent forming of the sheet was achieved, a hole being cleanly punched in the aluminum. In a second test, a similar aluminum sheet-mold assembly was placed in a 12 inch `diameter tank and the rifle ined as before. Some forming oi' the sheet was found. The area defined by the hole of mold was deformed to a considerable extent, but Was not punched out. ln a third test, a sheet-mold assembly was placed in a 24 inch diameter Huid vholder and this also subjected to the forming action of a 30-06 rifle bullet. Inspection of this sheet after the test Showed only a slight deformation of the aluminum covering the hole in the mold, this only marking the diameter of `the hole.

Satisfactory forming can be achieved in a given system using a relatively low energy projectile, e.g. from a small lbore rifle, revolver or other hand arm, by firing a number of successive shots into the liquid medium. By this action the desired forming is achieved in a stepwise fashion. This same multi-step technique can be used to carry out forming in large assemblies utilizing a more powerful initiator. Additionally, substantially simultaneous penetration of the liquidfby a number of high velocity projectiles can be used to advantage in certain forming operations.

Additionally, the degree of :forming that can be obtained from different projectiles of about the same mass and which are propelled at about the same initial velocity into comparable systems is dependent upon the shape of these driven masses. For example, with a tapered pointed projectile, such as a jacketed riile bullet, substantially uniform forming is achieved over a relatively long metalmold length. With a squatty, or hemispherically nosed, projectile of approximately the same mass, such as a shotgun slug, more pronounced lateral effects are noted near that portion of the mold where the energy first strikes the metal. A marked decrease in the amount of forming is achieved at the other end of the mold area which is removed from Ithis point of Ainitial contact of projectile and fluid.

The liuid to be used in the instant method can be selected from any of a wide variety of liquids which do not react with the material being formed or the mold and which in themselves are not affected adversely by the high speed projectiles. Particularly effective fluids are water, mineral oil, carbon tetrachloride, silicone oils, lorinated hydrocarbons, aqueous salt solutions and the For practical considerations, a layer of an inert material such as sand, can be placed in the bottom of the container which holds the mold and the mold then be placed thereon. Such a layer will serve to s-topthe projectile and prevent it from damaging the bottom ofthe container. Alternatively, a thick bottomed container or insertion of a thick metal plate into lthe bottom of fthe treatment vessel can be used. Additionally, a long column of liquid will in itself serve to `dissipate the energy of the moving mass.

in actual operation .the metal mold is placed in a container, preferably heavy-walled, and the metal to be formed, conforming generally to the shape of the mold,

is then placed adjacent to the molding surface. The container is then filled with a liquid up to a point at least above the top of the mold. A ballistic shock wave and cavitation generator, for example a 30-06 caliber rie, is then positioned above the container so that as the gun is tired, its Ibullet passes through 'the liquid in such a manner that the metal being formed is between the mold and this projectile. V

The thickness of metal which can be formed -by this method will be dependent both on the characteristics of the metal, the thermal state of the metal, and the shock energies imparted :to the liquid by the projectile. Ordinarily, with small arms this method will lbe limited to those metals having a thickness up to about 0.20 inch or more. To illustrate,..012 inch thick aluminum, 0.05 inch thick aluminum, .064 inch thick magnesium and .023 inch thick galvanized steel all were successfully formed in a inch diameter pipe mold immersed in a l2 inch diameter container of water by tiring a single 30-06 rie bullet at room temperature down through the pipe mold along its central axis.

However by employing projectiles possessing much higher kinetic energies and/ or by heating the metal, thickness considerably greater than 0.20 inch can be successfully formed by the instant method.

Successful forming of metals by this method is 4achieved utilizing one piece cylindrical molds, split molds, hat molds and other molds of a wide variety of intricate shapes. Additionally, holes of any shape can he punched into a metal utilizing a fiat or a shaped mold having a corresponding pattern hole therein. This method also can be used to achieve a press tit of a sleeve in a cylindrical hole or in a hole of other configuration which many times cannot readily be carried out by conventional press tit techniques.

The following examples will serve to fur-ther illustrate the method of the present invention but are not meant to llimit it thereto.

Example 1Y A cylindrical 4 foot long steelopen-topped container about l2 inches in diameter and having one inch thick walls was used as a fluid container. A layer of sand of about 4 inches thick was used to cover its bottom.

A cylindrical mold was made from a l5 inch length of 5 inch inside diameter -pipe having a 3,/8 inch wall thickness. A series of -iour holes (1 inch, 1/2 inch, 1A inch and 1/3 inch diameter) were drilled around the pipe at four intervals along the length ot the mold. Additional-ly, circumferential grooves Mt inch wide by 1/4 inch deep were cut into the inside Wall of the pipe between the series of spaced holes.

The mold was placed on end inside the container. A sheet of 0.012 inch thick aluminum was cut and rolled -to loosely lit within the mold. The tank was then tilled with water to a height of about 2 inches above the top of the mold.

A 30-06 riile was placed above the Water and positioned so that when tired its pointed tip bullet (10.6 grams mass, 2800 'ft/sec. initial velocity) would pass vertically downward through the mold along its center axis.

After tiring the rifle, the mold assembly was removed from the reservoir and examined. The aluminum sheet was found to have filled the contours ot`` the mold and was punched out at those spots where the mold contained the drilled holes.

In a second series of tests using the same apparatus and test technique, 0.025 inch, 0.042 inch and 0.064 inch thick magnesium sheet was subjected to ballistic forming. With this particular mold and specic projectiles as cavitation generator and ballistic shock wave former, the 0.025 inch magnesium was formed almost equally as well as the 0.012 inch aluminum.V The 0.042 inch and 0.064 inch magnesium sheets were formed into cylinders but only the l inch diameter holes had been punched out in these thicker materials.

Another run using 0.023 inch thick galvanized steel sheet as forming stock gave a resulting cylinder of approximately the same qual-ity as that produced from the 0.025 inch thick magnesium.

Example 2 A 21%; inch outside diameter copper tubing having a wall thickness of about 0.05 inch was placed into a 3 inch inside diameter, 1./4 inch thick Walled steel pipe. This assembly was then placed on end in a tank of Water and a 30-06 rie bullet fired through the pipe along its center axis. Examination of the so-treated copper tubesteel pipe assembly showed that an excellent press fitoi the tube within the pipe was obtained.

Example 3 A sheet of aluminum about 0.05 inch thick was fastened onto a Aflat plate-like mold having a number of holes placed therein. The mold with accompanying plate was placed in a 6 inch diameter tank iilled with machine oil. A 12 gauge shotgun was used to tire a hemispherical slug into the tank. This slug (28 grams Weight and 920 ft./sec. initial velocity) passed through the liquid in front of the aluminum sheet and travelled through the liquid along the entire length of the mold assembly.

Examination of the shock-treated metal showed holes in the aluminum corresponding to that of the hat mold.

Example 4 Utilizing the forming technique as in Example l and a mold containing several 1A inch grooves which were drilled to contain a number of small holes for release of the liquid, a sheet of 0.05 inch aluminum was formed using a 30-06 rie bullet as projectile. The formed product resulting from this treatment was a cylinder having ridges corresponding to the grooves in the pipe but these ridges were not perforated at those spaces corresponding to the holes in the mold.

In a second test, a 2 gauge shotgun slug was used as the projectile. The shape of the resulting cylinder in this case was substantially the same as that found for the previous test except that the ridges of the formed aluminum corresponding to the grooves near that portion of the mold which tirst was contacted by the shock wave from the penetrating projectile contained punched-out holes corresponding to the openings in the mold pattern.

Example 5 A sheet of 0.012 inch thick aluminum metal was rolled and placed into an 8 inch long cylindrical steel mold having an inside diameter of 2.75 inch.

The mold was tted on one side near the top with a 0.5 inch hole. Additionally below this hole there was an 0.25 inch groove machined into the inner wall around the diameter. in turn, a series of 0.125 inch holes, for liquid release, was drilled through the wall of the mold around this groove.

The aluminum sheet-mold assembly was placed on end in a 6 inch inside diameter Yby 24 inch long tank containing Water. The height of the water in the tank was about 3 inches above the top edge of the mold.

A bullet from a 32 caliber special rifle bullet (weight about 11.5 grams and initial velocity about 1900 feet/ second) was tired from a height of about 20 feet down through the center of the mold. After tiring, the moldaluminum sheet assembly was removed from the tank and inspected. The sheet Was found to be gently deformed with the metal being forced a small amount into the groove and holes.

The assembly was then replaced in the tank and a second bullet fired down through the center of the mold in the same manner as for the first shot. Examination of the mold assembly showed that the metal now lled the groove and had been pushed into the 0.50 inch hole to such an extent that it was almost pushed out.

Firing a third shot from the same rifle through the mold assembly in the tank was found to have forced the metal into the 0.125 inch liquid release holes around the groove. Also, the metal was punched out of the aluminum sheet at the 0.50 inch pattern hole in the mold,

Various modications can be made in the method of the instant invention without departing from the spirit or scope thereof for it is understood that I limit myself only as dened in the appended claims.

I claim:

l. A method of forming metals which comprises; immersing a mold within a liquid medium, positioning adjacent to said mold in said liquid medium a metal to be formed, said liquid medium being substantially unreactive with the metal to be formed and the mold and said liquid not being aected adversely by a projectile pa-ssing at high speed therethrough, passing a projectile through said liquid within said mold and in the vicinity of said metal being formed, said projectile passing through said liquid near the face of said metal opposite that facing said mold, said projectile moving through said liquid at a velocity which produces a high energy shock front in said liquid along with cavitation of the liquid behind the moving projectile and at such a. distance from said metal lbeing formed whereby said metal is forced into contact with said mold and thereby deformed in a predetermined manner by said contact with said mold.

2. A method of forming metals which comprises; immersing a mold within a liquid contained in a heavy walled container, said liquid being substantially nonreactive withithe mold and the metal to be formed and not being adversely affected by a projectile passing at high speed therethrough, placing said metal to be formed substantially in loose contact with the molding surface of said mold, said metal having a maximum thickness of about 0.200 inch and said metal conforming generally to the shape of said mold, passing a projectile through the liquid within said mold at a velocity sufficient to produce a high energy shock front in said liquid along With cavitation of the liquid behind the moving projectile, said projectile passing through the liquid near the face of said metal being formed opposite that which faces the molding surface and at a distance from said metal such that said high energy shock front and cavitation in said liquid urges said metal into conformity with the molding surface thereby deforming ysaid metal in a predetermined manner.

3. A method of producing walled openings in a metal which comprises; immersing a mold having walled openings within a liquid contained in a heavy-walled container,

said liquid being substantially non-reactive With the mold and the metal to have the openings punched therethrough and not being adversely affected by a projectile passing at high velocity therethrough, placing said metal to 'be punched in contact with the surface of said mold, said metal having a maximum thickness of about 0.200 inch, passing a projectile at a velocity suicient to produce a high energy shock front in said liquid along with cavitation of the liquid behind the moving projectile through said liquid within said mold in the vicinity of said metal to be punched, said projectile passing through the liquid within said mold parallel to said metal being punched and near the face of said metal opposite that which faces the mold surface and suiciently close to said metal whereby the high energy shock front and cavitation in said liquid forces said metal against said mold thereby punching openings in said metal the size and shape of which are defined by the walled openings of said mold.

4. A method of forming a metal which comprises; placing a metal to be formed near a mold surface, placing said metal and mold within a tank having a maximum diameter of about 12 inches, adding Water to said tank, said water filling said tank to a height of about 2 inches above said mold and metal, positioning a gun equivalent in power to about a 30-06 rifle above said tank, said gun being aimed t0 fire within said mold in said tank, firing lthe gun whereupon the projectile from said gun penetrates the water within said mold substantially parallel to said mold along its length, said projectile passing in the vicinity of said metal being formed and near the face of said metal opposite that which faces the molding surface of said mold, said projectile from said gun producing a high energy shock front and cavitation in said liquid suicient to force said metal against the molding surface of said mold and urging said metal into conformity with the molding surface of said mold `thereby deforming said metal in a predetermined manner.

5. The process as defined in claim 4 wherein the proj ectile is a riile bullet.

6. The process as defined in `claim 4 wherein the projectile is a shotgun slug.

References Cited in the file of this patent UNITED STATES PATENTS 30,647 Sharps Nov. 13, 1860 56,807 Shearman July 31, 1866 2,669,209 Hoffman Feb. 16, 1954 2,789,005 Foster E Apr. 16, 1957 

1. A METHOD OF FORMING METALS WHICH COMPRISES; IMMERSING A MOLD IN SAID LIQUID MEDIUM A METAL TO JACENT TO SAID MOLD IN SAID LIQUID MEDIUM A METAL TO BE FORMED, SAID LIQUID MEDIUM BEING SUBSTANTIALLY UNREACTIVE WITH THE METAL TO BE FORMED AND THE MOLD AND SAID LIQUID NOT BEING AFFECTED ADVERSELY BY A PROJECTILE PASSING AT HIGH SPEED THERETHROUGH, PASSING A PROJECTILE 